Purpose :
The retinal pigment epithelium (RPE) a monolayer of polarized cells that plays many essential roles in the maintenance and homeostasis of photoreceptor cells. The apical ends of RPE abut and engulf photoreceptor OS through phagocytosis whereas the basolateral sides lie on Bruch's membrane and transport nutrients, digested metabolic wastes, ions and water between the retina and the choroidal vasculature in the back of the eye. RPE provides the recycle of retinoids for the phototransduction pathway as well as the blood-retinal barriers. De-polarization of RPE may influence the functions of RPE in maintaining the homeostasis of the retina and choroid. Therefore, the purpose of this study is to investigate the RPE proteome changes under the de-polarized condition.

Methods :
The label-free LC-MS/MS analysis was used to the proteome samples from the polarized-RPE and the non-polarized RPE. The real-time RT-PCR analysis was used to confirm the de-polarization-influenced proteins. Phagocytotic ability, tight junction, and microvilli formation were evaluated in the polarized-RPE and the non-polarized RPE.

Results :
The label-free proteomic analysis identified 216 proteins, which are influenced by de-polarization condition. Six RPE specific proteins and 3 tight junction-related proteins were downregulated by depolarization condition and were confirmed the RNA expression in the polarized-RPE and the non-polarized RPE. The de-polarized RPE reduced 2.3-fold of phagocytosis ability and lose the tight junction. In addition, the microvilli were less in the de-polarized RPE than in the polarized PRE.

Conclusions :
RPE de-polarization can dramatically change the RPE gene expression and RPE biological functions. Our findings provided crucial information for investigating the role of RPE polarity in maintaining the homeostasis of the retina and choroid.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.